Friction weld coaxial connector and interconnection method

ABSTRACT

A coaxial connector for interconnection with a coaxial cable with a solid outer conductor by friction welding is provided with a monolithic connector body with a bore. A sidewall of the bore is provided with an inward annular projection angled toward a cable end of the bore. A sidewall of the inward annular projection and the sidewall of the bore form an annular friction groove open to a cable end of the bore. The annular friction groove is dimensioned with a taper at a connector end of the friction groove less than a thickness of a leading end of the outer conductor. The taper provides an annular material chamber between the leading end of the outer conductor, when seated in the friction groove, and the connector end of the friction groove.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of commonly owned co-pendingU.S. Utility patent application Ser. No. 12/951,558, titled “Laser WeldCoaxial Connector and Interconnection Method”, filed Nov. 22, 2010 byRonald A. Vaccaro, Kendrick Van Swearingen, James P. Fleming, James J.Wlos and Nahid Islam, currently pending and hereby incorporated byreference in its entirety.

BACKGROUND

1. Field of the Invention

This invention relates to electrical cable connectors. Moreparticularly, the invention relates to a coaxial cable connectorinterconnectable via friction welding.

2. Description of Related Art

Coaxial cable connectors are used, for example, in communication systemsrequiring a high level of precision and reliability.

To create a secure mechanical and optimized electrical interconnectionbetween the cable and the connector, it is desirable to have generallyuniform, circumferential contact between a leading edge of the coaxialcable outer conductor and the connector body. A flared end of the outerconductor may be clamped against an annular wedge surface of theconnector body via a coupling body. Representative of this technology iscommonly owned U.S. Pat. No. 6,793,529 issued Sep. 21, 2004 to Buenz.

Although this type of connector is typically removable/re-useable,manufacturing and installation is complicated by the multiple separateinternal elements required, interconnecting threads and relatedenvironmental seals.

Connectors configured for permanent interconnection via solder and/oradhesive interconnection are also well known in the art. Representativeof this technology is commonly owned U.S. Pat. No. 5,802,710 issued Sep.8, 1998 to Bufanda et al. However, solder and/or adhesiveinterconnections may be difficult to apply with high levels of qualitycontrol, resulting in interconnections that may be less thansatisfactory, for example when exposed to vibration and/or corrosionover time.

Competition in the coaxial cable connector market has focused attentionon improving electrical performance and long term reliability of thecable to connector interconnection. Further, reduction of overall costs,including materials, training and installation costs, is a significantfactor for commercial success.

Therefore, it is an object of the invention to provide a coaxialconnector and method of interconnection that overcomes deficiencies inthe prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention,where like reference numbers in the drawing figures refer to the samefeature or element and may not be described in detail for every drawingfigure in which they appear and, together with a general description ofthe invention given above, and the detailed description of theembodiments given below, serve to explain the principles of theinvention.

FIG. 1 is a schematic external isometric view of an exemplary embodimentof a coaxial connector installed upon a coaxial cable with a couplingnut spaced away from the connector along the cable forconnector-to-cable interconnection.

FIG. 2 is a schematic isometric view of the coaxial connector of FIG. 1installed upon a coaxial cable, with the coupling nut seated upon thecoaxial connector.

FIG. 3 is a schematic isometric view of the coaxial connector of FIG. 1.

FIG. 4 is a schematic cross section side view of FIG. 2.

FIG. 5 is an enlarged view of area A of FIG. 4.

FIG. 6 is a schematic exploded isometric partial cut-away view of theconnector and cable of FIG. 1.

FIG. 7 is a schematic isometric partial cut-away view of the connectorbody of FIG. 5.

FIG. 8 is a schematic isometric view of an alternative connector bodywith notches on a flange of the connector body.

FIG. 9 is a schematic isometric view of an alternative connector bodywith longitudinal knurls on the connector body outer diameter.

FIG. 10 is a schematic isometric cut-away view of the overbody of FIG.5.

FIG. 11 is an enlarged view of area B of FIG. 4.

FIG. 12 is a schematic cross section side view of an alternativeoverbody with corrugation on an inner diameter of the cable end.

FIG. 13 is a schematic cross section side view of an alternativeoverbody with a stepped surface on an inner diameter of the cable end.

FIG. 14 is a schematic cross section side view of a coaxial connectorembodiment with an inner conductor end cap.

DETAILED DESCRIPTION

Aluminum has been applied as a cost-effective alternative to copper forthe conductors in coaxial cables. However, aluminum oxide surfacecoatings quickly form upon air-exposed aluminum surfaces. These aluminumoxide surface coatings may degrade traditional mechanical, solder and/orconductive adhesive interconnections.

The inventors have recognized that increasing acceptance of coaxialcable with solid outer conductors of aluminum and/or aluminum alloyenables connectors configured for interconnection via friction weldingbetween the outer conductor and a connector body which may also be costeffectively provided, for example, formed from aluminum and/or aluminumalloy.

An exemplary embodiment of a friction weldable coaxial connector 2 isdemonstrated in FIGS. 1-4. As best shown in FIG. 4, a unitary connectorbody 4 is provided with a bore 6 dimensioned to receive the outerconductor 8 of a coaxial cable 9 therein. An inward projecting shoulder10 angled toward a cable end 12 of the connector body 4 forms an annularfriction groove 14 open to the cable end 12. As best shown in FIG. 5,the friction groove 14 is dimensioned to receive a leading edge of theouter conductor 8 therein, a thickness of the outer conductor 8preventing the outer conductor 8 from initially bottoming in thefriction groove 14, forming an annular material chamber 16 between theleading edge of the outer conductor 8 and the bottom of the frictiongroove 14, when the outer conductor 8 is initially seated within thefriction groove 14.

One skilled in the art will appreciate that connector end 18 and cableend 12 are applied herein as identifiers for respective ends of both theconnector and also of discrete elements of the connector describedherein, to identify same and their respective interconnecting surfacesaccording to their alignment along a longitudinal axis of the connectorbetween a connector end 18 and a cable end 12.

The bore sidewall 20 may be diametrically dimensioned to create afriction portion 22 proximate the friction groove 14. The frictionportion 22 creates additional interference between the bore sidewall 20and the outer diameter of the outer conductor 8, to increase frictionduring friction welding.

Prior to interconnection via friction welding, also known as spinwelding, the cable end 12 may be prepared, as best shown in FIG. 6, bycutting the cable 9 so that the inner conductor 24 extends from theouter conductor 8. Also, dielectric material 26 between the innerconductor 24 and outer conductor 8 may be stripped back and a length ofthe outer jacket 28 removed to expose desired lengths of each, includinga sacrificial portion of the outer conductor 8 which is consumed duringthe friction welding process.

To initiate friction welding, the connector body 4 is rotated withrespect to the outer conductor 8 during seating of the leading edge ofthe outer conductor 8 within the friction portion 22 and into thefriction groove 14, under longitudinal pressure. During rotation, forexample at a speed of 250 to 500 revolutions per minute, the frictionbetween the leading edge and/or outer diameter of the outer conductor 8and the friction portion 22 and/or friction groove 14 of the bore 6generate sufficient heat to soften the leading edge and/or localizedadjacent portions of the outer conductor 8 and connector body 4, forgingthem together as the sacrificial portion of the outer conductor 8 formsa plastic weld bead that flows into the material chamber 16 to fuse theouter conductor 8 and connector body 4 together.

Because the localized abrasion of the friction welding process can breakup any aluminum oxide surface coatings in the immediate weld area, noadditional care may be required with respect to removing or otherwisemanaging the presence of aluminum oxide on the interconnection surfaces.

An overbody 30, as shown for example in FIG. 10, may be applied to theconnector body 4 as an overmolding of polymeric material. The overbody30 increases cable to connector torsion and pull resistance. Theoverbody 30 may also provide connection interface structure at theconnector end 18 and further reinforcing support at the cable end 12,enabling significant reductions in the size of the connector body 4,thereby reducing overall material costs.

Depending upon the applied connection interface 31, demonstrated in theexemplary embodiments herein as a standard 7/16 DIN interface, theoverbody 30 may be provided with an overbody flange 32 and longitudinalsupport ridges 34 for a coupling nut 36. The coupling nut 36 is retainedupon the support ridges 34 at the connector end 18 by an overbody flange32 and at the cable end 12 by a retention spur 38 provided on at leastone of the support ridges 34. The retention spur 38 may be angled towardthe connector end 18, allowing the coupling nut 36 to be placed over thecable 9 initially spaced away from the coaxial connector 2 duringinterconnection (see FIG. 1), but then allowing the coupling nut 36 tobe passed over the retention spur 38 and onto the support ridges 34 fromthe cable end 12, to be thereafter retained upon the support ridges 34by the retention spur(s) 38 (see FIG. 2) in close proximity to theconnector interface 31 for connector to connector mating. The supportridges 34 reduce polymeric material requirements of the overbody 30while providing lateral strength to the connector/interconnection 2 aswell as alignment and retention of the coupling nut 36.

The overbody 30 may also extend from the connector end 18 of theconnector body 4 to provide portions of the selected connector interface31, such as an alignment cylinder 39 of the 7/16 DIN interface, furtherreducing metal material requirements of the connector body 4.

The overbody flange 32 may be securely keyed to a connector body flange40 of the connector body 4 and thereby with the connector body 4 via oneor more interlock apertures 42 such as holes, longitudinal knurls 43,grooves, notches 45 or the like provided in the connector body flange 40and/or outer diameter of the connector body 4, as demonstrated in FIGS.7-9. Thereby, as the polymeric material of the overbody 30 flows intothe interlock apertures 42 during overmolding, upon curing the overbody30, for example as shown in FIG. 10, is permanently coupled to androtationally interlocked with the connector body 4.

As best shown in FIG. 11, the cable end 12 of the overbody 30 may bedimensioned with an inner diameter friction surface 44 proximate that ofthe coaxial cable outer jacket 28, enabling polymeric friction weldingbetween the overbody 30 and the outer jacket 28, as the connector body 4and outer conductor, thereby eliminating the need for environmentalseals at the cable end 12 of the connector/cable interconnection. Duringfriction welding, the coaxial connector 2 is rotated with respect to thecable 9. Friction between the friction surface 44 and the outer diameterof the outer jacket 28 heats the respective surfaces to a point wherethey begin to soften and intermingle, sealing them against one another.To provide enhanced friction and allow voids for excess flow due tofriction displacement and add key locking for additional strength, theouter jacket 28 and/or the inner diameter of the overbody 30 may beprovided as a series of spaced apart annular peaks of a contour patternsuch as a corrugation 46, as shown for example in FIG. 12, or a steppedsurface 48, as shown for example in FIG. 13. Alternatively, the overbody30 may be sealed against the outer jacket 28 with an adhesive/sealant ormay be overmolded upon the connector body 4 after interconnection withthe outer conductor 8, the heat of the injected polymeric materialbonding the overbody 30 with and/or sealing against the outer jacket 28.

The inner conductor 24 extending from the prepared end of the coaxialcable 9 may be selected to pass through to the connector end 18 as aportion of the selected connection interface 31, for example as shown inFIG. 4. If the selected coaxial cable 9 has an inner conductor 24 thathas a larger diameter than the inner conductor portion of the selectedconnector interface 31, the inner conductor 24 may be ground at theconnector end 18 to the required diameter.

Although a direct pass through inner conductor 24 advantageouslyeliminates interconnections, for example with the spring basket of atraditional coaxial connector inner contact, such may introduceelectrical performance degradation such as PIM. Where the innerconductor 24 is also aluminum material some applications may require anon-aluminum material connection point at the inner contact/innerconductor of the connection interface 31. As shown for example in FIG.14, a center cap 50, for example formed from a metal such as brass orother desired metal, may be applied to the end of the inner conductor24, also by laser or friction welding. To apply the center cap 50, theend of the inner conductor 24 is ground to provide a pin correspondingto the selected socket geometry of the center cap 50. To allow materialinter-flow during welding attachment, the socket geometry of the centercap 50 and or the end of the inner conductor 24 may be formed to providematerial gaps as described with respect to the material chamber 16described herein above.

One skilled in the art will appreciate that the connector andinterconnection method disclosed has significant material costefficiencies and provides a permanently sealed interconnection withreduced size and/or weight requirements.

Table of Parts 2 coaxial connector 4 connector body 6 bore 8 outerconductor 9 cable 10 shoulder 12 cable end 14 friction groove 16material chamber 18 connector end 20 bore sidewall 22 friction portion24 inner conductor 26 dielectric material 28 outer jacket 30 overbody 31connection interface 32 overbody flange 34 support ridge 36 coupling nut38 retention spur 39 alignment cylinder 40 connector body flange 42interlock aperture 43 longitudinal knurl 44 friction surface 45 notch 46corrugation 48 stepped surface 50 center cap

Where in the foregoing description reference has been made to materials,ratios, integers or components having known equivalents then suchequivalents are herein incorporated as if individually set forth.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin considerable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details, representativeapparatus, methods, and illustrative examples shown and described.Accordingly, departures may be made from such details without departurefrom the spirit or scope of applicant's general inventive concept.Further, it is to be appreciated that improvements and/or modificationsmay be made thereto without departing from the scope or spirit of thepresent invention as defined by the following claims.

1. A method for interconnecting a coaxial connector with a solid outerconductor coaxial cable, comprising the steps of: providing a monolithicconnector body with a bore; a sidewall of the bore provided with aninward annular projection angled toward a cable end of the bore; asidewall of the inward annular projection and the sidewall of the boreforming an annular friction groove open to a cable end of the bore;inserting a leading end of the coaxial cable into the bore, until aleading end of the solid outer conductor seats within the frictiongroove; rotating the connector body about a longitudinal axis of theleading end of the coaxial cable, while applying longitudinal forcedriving the friction groove against the leading end of the outerconductor.
 2. The method of claim 1, wherein the outer conductor and theconnector body are each one of aluminum and aluminum alloy material. 3.The method of claim 1, wherein the friction groove is provided with anannular material chamber at a connector end of the friction groove. 4.The method of claim 1, wherein the rotation and longitudinal force areapplied until heat sufficient to melt the leading end of the outerconductor is generated.
 5. The method of claim 1, wherein the rotationand longitudinal force generate a friction weld between the outerconductor and the connector body.
 6. The method of claim 1, furtherincluding the step of overmolding the connector body attached to the endof the coaxial cable with a polymeric overbody.
 7. The method of claim1, further including the steps of preparing the leading end of the cableend prior to insertion into the bore by removing a portion of the outerconductor so that an inner conductor extends therefrom, removing aportion of a dielectric material between the inner conductor and theouter conductor such that when the leading edge of the outer conductorcontacts the inward annular projection, the friction groove does notcontact the dielectric material; and stripping back a portion of ajacket from the outer conductor.
 8. The method of claim 1, furtherincluding providing an overbody of polymeric material upon an outerdiameter of the connector body, the overbody extending from the cableend of the connector body, an inner diameter of the overbody extendingfrom the cable end of the connector body provided as a friction surfacedimensioned for an interference fit upon an outer diameter of a jacketof the coaxial cable.
 9. The method of claim 8, wherein the rotation andlongitudinal force form a friction weld between the outer conductor andthe connector body and between the overbody and the jacket of thecoaxial cable.